Year	% of total
1970	2.61819151758208
1971	4.2325203918581185
1972	3.593785320414708
1973	3.3769189442445584
1974	3.4542111066125614
1975	3.294637918130544
1976	3.6920163197776037
1977	3.6020208900569917
1978	3.872826463013797
1979	3.426805469419611
1980	2.702437410457179
1981	4.278703126657411
1982	4.186633642668562
1983	4.352700528912922
1984	5.401479849501629
1985	5.928316394241939
1986	6.661686391873604
1987	5.32426415247177
1988	7.462391529605224
1989	7.0040557577859
1990	9.421487603305785
1991	10.278745644599303
1992	11.151079136690647
1993	12.037037037037036
1994	11.971830985915492
1995	11.326860841423949
1996	11.24087591240876
1997	12.518853695324283
1998	14.262820512820513
1999	15.175718849840255
2000	16.585365853658537
2001	14.245416078984485
2002	14.124293785310735
2003	26.954177897574123
2004	24.937027707808564
2005	21.68141592920354
2006	18.330308529945555
2007	22.657952069716774
2008	12.186788154897494